The present invention relates to an improved process for preparing 11.beta.-hydroxy steroids.
As is known, 11.beta.-hydroxy steroids having antiinflammatory activity (such as, for example, the corticoids: hydrocortisone, prednisolone, dexamethasone, betamethasone, prednylidene and flurandrenolone) are produced from naturally occurring steroids (such as diosgenin) by means of a very expensive, multistage partial synthesis.
Within the multistage synthesis of these compounds, the microbiological introduction of the 11.beta.-hydroxy group into the steroid skeleton is normally the most expensive synthesis step and also the one wherein most of the losses are incurred due to the formation of by-products.
A process was developed in 1966 whereby the yield in the 11.beta.-hydroxylation of 11-deoxy-17.alpha.-hydroxy steroids of the pregnane series was substantially increased by esterifying the 17.alpha.-hydroxy group, then hydroxylating using fungi of the genus Curvularia and saponifying the thus-obtained 11.beta.-hydroxy-17.alpha.-acyloxy steroids (German Pat. No. 1,618,599). The 11-deoxy 17.alpha.-acyloxy steroids utilized as the starting compounds for this known process could be conventionally prepared, in turn, by chemical hydrolysis of 11-deoxy steroids of Formula II below. Disadvantageously, three-stage processes were necessarily required.